Chapter 39

167Beale,Bioplasm, p. 177.Max Schultze, inStricker’s Handbuch, p. 134. Comp.Stilling,Nervenprimitiv-Faser, p. 133.Arndt,Archivfür mikros. Anat., 1868, p. 512; and 1869, p. 237. Weighty as these authorities are, their view is questionable—firstly, because the forms of these cells are too constant and definite in particular places to result from the union of fibrils coming from various origins; but secondly, and mainly, because the teaching of Development is opposed to it.168Robin,Anat. et Physiol. Cellulaires, p. 335.169Archives de Physiologie, 1872, p. 268.170The fact of the existence of cells in the white substance is one which is very difficult of interpretation on the current hypotheses. The cells are found in regular columns and irregularly scattered.Bollthinks that while in the white substance of both cerebrum and cerebellum there are true nerve-cells as well as connective corpuscles, in the cord there are only the latter. But hitherto there has been no decisive test by which a nerve-cell can be distinguished from a connective corpuscle.171Monthly Journal of Micros. Science, XI. 219. This accords with whatKupffersays respecting the entire absence of cells in the earliest stages observed by him in the sheep. The white substance of the spinal cord he describes as soft, transparent, and gelatinous, in which dark points are visible; these dark points are seen in longitudinal sections to arise from the fibrillation of the substance.—BidderundKupffer,Op. cit., p. 111.172Weismann,Die nachembryonale Entwick. der Musciden, in theZeitschrift für Wissen. Zoologie, 1864, Bd. XIV. Heft III.173The suggestion in the text has since received a striking confirmation in the observations ofSigmund Mayeron the regeneration of nerves. The nerve when divided rapidly undergoes fatty degeneration, which is succeeded by a transformation of the myeline and axis cylinder into a homogeneous mass; in this resolved pulp new longitudinal lines of division appear, which subsequently become new fibres, and new nuclei are developed in the remains of the untransformed substance.—Archiv für Psychiatrie, Bd. VI. Heft II.174Strong confirmation of various statements in the text, since they were written, has been furnished by the researches ofEichhorst, published inVirchow’s Archiv, LXIV. Our knowledge of the development of nerve-tissue in human embryos is so scanty that these researches have a great value.Eichhorstdescribes the striation of the cells in the cord to begin only at the fourth month; up to this time they are, what I find most invertebrate cells to be, granular, not fibrillar. There is very slight branching of the cell processes until the ninth or tenth month, when the multipolar aspect first appears; the cells are unipolar up to the end of the fourth month. The connection between the white columns and the gray columns is very loose up to the fifth month; and the two are easily separated. Subsequently the union is closer. The substance of the white columns readily separates into bundles and fibres, but that of the gray columns falls into a granular detritus if attempted to be teased out with needles. But after the fifth month this is no longer so. Instead of a granular detritus there appears a network of fine fibres and fibrils. Although the white posterior columns are developed before the fifth month, not a single cell can be seen in the posterior gray columns until the second half of the ninth month. (Yet the fibres are imagined to arise in the cells!) The passage from the granular to the fibrillar state is the same in the cell substance and the neuroglia. The nerve-fibre, as distinguished from a naked axis cylinder, does not appear till the fourth month. It is at first a bipolar prolongation of the nucleus. As it elongates, the nucleus seems to sitonit, and so loosely that it is easily shifted away by pressure on the covering glass. Finally the fibre separates entirely from the nucleus, andthenbegins to clothe itself with the medullary sheath. Very curious is the observation that so long as the axis cylinder is naked it is never varicose, but with the development of the medulla the primitive axis becomes fluid.175Mayer,Op. cit., 393. I cannot, however, agree withMayerwhen he says that the continuity of a nerve-fibre with a cell hasneverbeen distinctly shown (p. 395); in the Invertebrata and in the Electric fishes such a continuity is undeniable; and it has occasionally been seen in Vertebrata.176Ranvier, in theComptes Rendus, 1875, Vol. LXXXI. p. 1276. This observation throws light on the fact that cell processes are sometimes seen entering nerve-roots (§124).The very remarkable observations of Mr.F. Balfour,On the Development of the Spinal Nerves in Elasmobranch Fishes(Philos. Trans., Vol. CLXVI. p. 1), show that the spinal root, ganglion, and nerve-trunk arise from histological changes in a mass of cells at first all alike;notthat ganglion-cells are formed and from their processes elongate into fibres. The nerve, he says, forms a continuation of its root rather than of its ganglion (p. 181); which accords withRanvier’sview.177In theHandbuch der menschlichen AnatomieofW. Krause, which has just appeared, I am pleased to find a similar view, p. 376.178On this point consultAxel KeyandRetzius, in theArchiv für mikros. Anat., 1873, p. 308, where the nutritive disturbance is assigned to the fact that the lymph can no longer take its normal course.Waller’sobservations on the degeneration of the optic nerves, with preservation of the integrity of the retina, after division of the nerves (Proceedings of Royal Society, 1856, p. 10), cannot be urged in support of his view, becauseBerlinandLebert’sobservations are directly contradictory of his.SaemischundGraefe,Handbuch der Augenheilkunde, II. 346. It is said byKrenchelthat if the nerves be divided, so as to prevent disturbances in the circulation, no peripheral degeneration takes place (cited byEngelmanninPflüger’s Archiv, 1875, p. 477).179Schiff,Lehrbuch der Physiologie, pp. 120, 121.180Kölliker,Gewebelehre, 317.Schwalbe,Archiv für mikros. Anat., 1868, p. 51.181I was first shown this in 1858 by the late Prof.Harlessin Munich, who at the same time showed me that the nerve thus bared of its sheath, if left some hours in gastric juice, split up into regular discs, like the sarcous elements of muscles.182Stieda,Bau des centralen Nervensystem der Amphibien und Reptilien, 1875, p. 41.183Butzke, inArchiv für mikroskopische Anatomie, Bd. III. Heft 3, p. 596.184Except in the rare cases where there is anastomosis of the muscle-fibres; as, for example, in the heart. [According toEngelmann’sremarkable researches, the muscles of the heart form a continuum, so that irritation is propagated from one to the other:Pflüger’s Archiv, 1875, p. 465. This is indubitably the case in the embryonic heart, asEckhardpointed out.] This I hold to be the main cause of its rhythmic pulsation after removal from the body. Whatever influence the ganglia may have in exciting this pulsation, such influence would be powerless were not the muscles so connected; as may be seen in the other organs which are richly supplied with ganglia, yet do not move spontaneously; and in organs (such as the ureter or the embryonic heart, and the hearts of invertebrata) which move spontaneously, yet have no ganglia.185Schröder van der Kolk,Bau und Funktionen der Med. Spinalis, p. 67.186It is very instructive to learn that for some six months or so the rat is quite incapable of correctlylocalizingthe pain.187Vulpian,Leçons sur le Système Nerveux, p. 288. The experiment has been confirmed byRosenthal, and byBidder(Archiv für Anatomie, 1865, p. 246), who first (in 1842) attempted this union of different nerves, but arrived at negative results; as didSchiff(Lehrbuch der Physiol, 1859, p. 134) andGlugeetThiernesse(Annales des Sciences Naturelles, 1859, p. 181).188Sachs, in theArchiv für Anat., 1874, pp. 195,sq.189Laplace,Essai Philos. sur les Probabilités, p. 239.190The mode of termination of nerves in muscles is still a point on which histologists disagree; probably because there is no abrupt termination, but a blending of the one tissue with the other. In the Tardigrades, for example, there is actually no appreciable distinction between nerve and muscle at the point of insertion of the nerve; and if in the higher animals there is an appreciable difference between nerve and muscle, there is an inseparable blending of undifferentiated substance at their point of junction. [According toEngelmann’srecent researches, there seems good reason to suppose that muscles are composed of contractile substance and a substance which is a modification of axis-cylinder substance; the first being doubly refracting, the second isotropic:Pflüger’s Archiv, 1875, p. 432.]191Schiff,Lehrbuch, p. 73.192Freusbergobserved that the reflex movements in the legs of a dog whose spine had been divided were considerably lessened after food or drink. They fell from 95 to 46 pendulum-beats in a minute after alitreof water had been drunk. See his instructive memoir,Reflex-Lähmungen beim Hunde, inPflüger’s Archiv, 1874, p. 369.193M.Herzenthus describes the effects of stimulating the vagus with varying intensities: “Si l’on se sert de l’appareil de Dubois Raymond, on commence par appliquer une irritation tellement faible qu’elle ne produit aucun effet; on rapproche alors peu à peu lea deux bobines de l’appareil avec le plus grand soin, par fractions de centimètres, parmillimètress’il le faut, et l’on trouve ainsi le degré d’irritation qui accelère les battements du cœur et qui produit le maximum de pulsations dans l’unité de temps admise pour l’expérience. Quand on est là il suffitd’un millimètrede plus pour faire disparaître l’augmentation, un autre millimètre peut produire une diminution, et untroisièmepeut arrêter le cœur complètement. En reculant alors, en éloignant peu à peu les deux bobines,on rètourne à la force qui produit l’augmentation des battements.”Herzen,Expériences sur les Centres Modérateurs de l’Action Réflexe, 1864, p. 68. There have been serious doubts thrown on these experiments; but several experimenters have confirmed their exactness. Quite recently they have been confirmed byBulgheri,Il Morgagni, VIII.; and byArloingandTripier,Archives de Physiologie, 1872, IV. p. 418. It must be confessed, however, that the whole subject of the heart’s innervation is at present very imperfectly understood.194Cayrade,Recherches sur les Mouvements Réflexes, 1864, p. 58.195A frog’s brain is removed, and the body then suspended by the lower jaw, the legs are allowed to dip into a slightly acidulated liquid, the chemical action of which stimulates the skin.196I saw a patient in the BerlinCharitéwhose face and left hand were in a constant state of convulsive twitching, but no sooner was a scar on the left hand (where the nerve had been divided) firmly pressed than the twitchings ceased, andpainwas felt; on removal of the pressure, pain ceased and the twitchings returned.197Pflüger’s Archiv, 1875. No one interested in the Reflex Theory should omit a careful study of the papers byFreusbergandGoltz. I have drawn freely from them.198SirJames Pagethas an interesting collection of facts which illustrate this Law of Arrest, in his paper on “Stammering with other Organs than those of Speech,”British Medical Journal, 1868, Vol. II. p. 437, reprinted in hisClinical Lectures and Essays, 1875, p. 77.199Archives de Physiol., 1868, p. 157.200West Riding Lunatic Asylum Reports, 1874, p. 200.201Claude Bernard,Système Nerveux, I. 383.202See the excellent remarks of Dr.Lauder Bruntonon this point in his paper on Inhibition in theWest Riding Lunatic Asylum Reports, 1874, p. 180.203The interesting question of interference has been experimentally treated byWundtin his recently publishedMechanik der Nerven, 1876, and theoretically as wave-movement byMedem,Grundzüge einer exakten Psychologie, 1876.204On the distinction between first notions and theoretic conceptions, seeProblems of Life and Mind, Vol. II. p. 277.205Not transcendental anda priori, as Kant teaches; but immanent in Feeling.206The reader will understand that although mechanical relations are modes of Feeling, as all other relations are, yet their aspect is exclusively objective, referring to objects ideally detached from subjects.207Antoine Cros,Les Fonctions supérieures du Système nerveux, 1875, p. 85.208The solution offered in the present chapter was first offered inProblems of Life and Mind, 1875, II. 465,sq.I mention this because since the publication of that volume other writers have expressed the same ideas, sometimes using my language and illustrations: e. g. M.Tainein theRevue Philosophique, January, 1877, art.,Les Vibrations cérébrales et la Pensée.209Problems of Life and Mind, Vol. II. pp. 443 and 482.210“The retinal image is the last effect known of the action of objects on us; what happens beyond the retina we know not; our knowledge of the objective process has at present here its limit.”—Ewald Hering,Beiträge zur Physiologie, 1862, p. 166. That is to say, we have a definite translation of the process in geometric terms as far as the retina, and thence onwards Geometry fails us, and Neurology and Psychology are invoked.211CompareProblem II.Chap. IV.212“Das Bewusstwerden ist nichts Anderes als ein weiter fortgeschrittenes Erinnern oder Neuwerden des von aussen aufgenommenen Wissens, ein innerliches Wissen dieses Wissens oder ein in sich reflectirtes Wissen.”—Jessen,Versuch einer Wissenschaftlichen Begründung der Psychologie, 1855, p. 477.213In common language a stone or a tree is said to be unconscious; but this is an anthropomorphic extension of the term. In strictness we should no more speak of unconsciousness outside the sphere of Sentience than of darkness outside the sphere of Vision.214The contraction may be effected in the eye out of the organism. See p.229. It is then no reflex.215Glasgow Medical Journal, 1857, p. 451. See also further on,noteto p.426.216Mayer,Die Elementarorganisation des Seelenorgans, p. 12, is the authority for the last statement.217Allgemeine Zeitschrift für Psychiatrie, Bd. 31, p. 711.218Aubert,Grundrüge der physiol. Optik, 1876, p. 633. “The accommodative movement of the eye is to be considered voluntary. It is true we contract the pupil without being conscious of the contraction of muscular fibres,but this holds good for every voluntary movement. When a person raises the tone of his voice he is not conscious that by muscular contraction he makes his chordæ vocales more tense; he attains his object without being aware of the means by which he does so. The same is applicable to accommodation for near objects and to the contraction of the pupil accompanying it. The fact thatthis last is only an associated movement does not deprive it of its voluntary character, for there is perhaps no single muscle which can contract entirely by itself.”Donders,On the Anomalies of Accommodation, 1864, p. 574. ProfessorBeerof Bonn has the rare power of contracting or dilating the pupils of his eye at will; here ideas act as motors. When he thinks of a very dark space the pupil dilates, when of a very bright spot the pupil contracts. (Noble,The Human Mind, 1858, p. 124.) I believe this to be only an exaggerated form of the normal tendency. In all of us the mechanism is so disposed that the feelings of dilatation are associated with feelings (and consequently ideas) of darkness; and by this association a reversal of the process obtains, so that the idea of darkness calls up the feeling it symbolizes.219Spencer,Principles of Psychology, I. 499.220Descartesexpressly calls them sensitive machines. He refuses them Thought, but neither “la vie ou le sentiment.” He adds, “Mon opinion n’est pas que les bêtes voient comme nous lorsque nous sentons que nous voyons.”—Œuvres, IV. p. 339. This example is cited by him in proof of human automatism: “Que ce n’est point par l’entremise de notre âme que les yeux se ferment, puisque c’est contre notre volonté, laquelle est sa seule ou du moins sa principale action; mais c’est à cause que la machine de notre corps est tellement composée que le mouvement de cette main vers nos yeux excite un autre mouvement en notre cerveau qui conduit les esprits animaux dans les muscles qui font abaisser les paupières.” All indeed that we assign to Sensibility, he assigns to these hypothetical animal spirits, and thence he concludes, “Qu’il ne reste rien en nous que nous devions attribuer à notre âme sinon nos pensées.”—Les Passions de l’Âme, art. 13 and 17. Comp.Discours de la Méthode, partie iv.221Descartescompares the animal mechanism to that of the grottos and fountains at Versailles, the nerves to the water-tubes:—“Les objets extérieurs qui par leur seul présence, agissent contre les organes des sens, et qui par ce moyen, la déterminent à se mouvoir en plusieurs diverses façons, selon comme les parties du cerveau sont disposées, sont comme les étrangers, qui entrant dans quelques unes des grottes de ces fontaines causent euxmêmes sans y penser les mouvements qui s’y font en leur présence: car ils n’y peuvent entrer qu’en marchant sur certains carreaux tellement disposés, que s’ils approchent d’une Diane qui se baigne, ils la font cacher dans les roseaux; et s’ils passent outre pour la poursuivre, ils feront venir vers eux un Neptune qui les menacera de son trident; ou s’ils vont de quelque autre costé, ils en feront sortir un monstre marin qui leur vomira de l’eau contre la face.”—Traité de l’Homme, 1664, p. 12. Ingenious as the comparison is, it only illustrates how machines may be constructed to imitate animal actions. Diana always hides herself when a certain spot is trodden upon; and Neptune always appears when another spot is trodden upon. There is no fluctuation, no sensibility discerning differences and determining variations. Compare the following experiment: A monkey was placed on the table and a shrill whistle made close to its ear: “Immediately the ear was pricked and the animal turned with an air of intense surprise, with eyes widely opened and pupils dilated, to the direction whence the sound proceeded. On repetition of the experiment several times, though the pricking of the ear and the turning of the head and eyes constantly occurred, the look of surprise and dilatation of the pupils ceased to be manifested.”—Ferrier,The Functions of the Brain, 1876, p. 171. A mechanical monkey would always have reacted in precisely the same way on each stimulus.222Printed in theFortnightly Review, November, 1874, from which all my citations are made.223Schiff,Lehrbuch der Physiol., 1858, p. 212.Hermann,Physiology, translated byGamgee, 1875, p. 511.224Meanwhile the reader is referred toSchröder van der Kolk,Pathologie der Geisteskrankheiten, 1863, p. 51; orJessen,Physiologie des menschlichen Denkens, 1872, p. 66.225Griesinger,Les Maladies Mentales, p. 96.226M.Luyscites the case of a patient who conversed quite rationally with a visitor “sans en avoir conscience, et ne se souvenait de rien”; and he draws the extraordinary conclusion that the conversation “s’opérait en vertu des forces réflexes.”—Études de Physiologie et de Pathologie Cérébrales, 1874, p. 117. Is it not obvious that the patient must have been conscious at the time, though the consciousness vanished like that in a dream? The persistent consciousness is the continuous linking on of one state with previous states—the apperception of the past.227Abercrombie,Inquiries concerning the Intellectual Powers, 1840, p. 151.Wigan,The Duality of the Mind, 1844, p. 270.Despine,La Psychologie Naturelle, 1868, I. 54.228Dr.Hughlings Jacksonhas quite recently cited some curious examples in his own practice. SeeWest Riding Lunatic Asylum Reports for 1875.229Problems, Vol. II. p. 478,sq.230“Le sentiment fait naître le mouvement, et le mouvement donne naissance au sentiment.”—Van Deen,Traités et Découvertes sur la Moëlle Épinière, 1841, p. 102.231Dr.Carpentertells a similar story of AdmiralCodrington, who, when a midshipman, could always be awakened from the profoundest slumber if the word “signal” were uttered; whereas no other word disturbed him.232Compare an interesting personal example given byJouffroy, quoted in SirW. Hamilton’sLectures, I. 331.233Lancet, 10th July, 1858.234Marshall HallinPhilos. Trans., 1833.Lectures on the Nervous System and its Diseases, 1836.New Memoir on the Nervous System, 1843.235Müller,Physiology, I. 721.236It is better simply to remove the brain, than to remove the whole head, which causes a serious loss of blood. An etherized animal may be operated on with ease and accuracy. For many experiments, mere division of the spinal cord is better than decapitation. Great variations in the results must be expected, because the condition of the animal, its age and sex—whether fasting or digesting—whether the season be spring or summer—and a hundred other causes, complicate the experiment.237Volkmann, quoted byPflüger.238Unzer,The Principles of Physiology(translated for the Sydenham Society), p. 235.239Even so eminent an investigator asGoltzhas fallen into this confusion. He introduces an experiment to prove that the brainless frog is insensible to pain by the words “when an animal, placed under circumstances which would be very painful, makes no movement, although quite capable of moving, the least we can say is that it is improbable that the animal has sensation” (Nervencentren des Frosches, p. 127). I need not discuss the proof itself, having already done so inNature, Vol. IX. p. 84. The point to which I wish to call attention is the confusion of insensibility in general with insensibility to pain.240SeeDuchenne,De Électrisation localisée, p. 398.Griesingercites various examples of insane patients who have burned the flesh off their bones while manifesting a total indifference to these injuries.Maladies Mentales, p. 94.Falretsays, “Nous avons vu plusieurs fois des aliénés s’inciser, s’amputer eux-mêmes diverses parties du corps sans paraître ressentir aucune souffrance.”Leçons cliniques de Médicine Mentale, 1854, I. 189. Patients incapable of feeling the contact of a hot iron with their skin have felt subjective burnings in the skin thus objectively insensible.241Cros,Les Fonctions supérieures du Syst. nerveux, 1875, p. 27.242Virchow’s Archiv, Bd. XXVIII. p. 30.243The idea of afixed anatomical mechanismfor reflexion, such as that of an excito-motory system, is completely refuted by the fact that the gray substance may anywhere be cut sway, and yet so long as a small bridge of gray substance remains the stimulation will be propagated through it. The idea of afixed pathwayis also refuted by the fact of the variations in the reflex responses, and the necessary irradiation even for very simple reflexes. Take, for example, that of breathing. An irritation of the bronchial filaments is transmitted by the pneumogastric to its centre in the medulla oblongata; from this, however, it is immediately irradiateddownwardsto the cervical and dorsal regions, which innervate the muscles of chest and diaphragm, andupwardsto the brain, whether the stimulation awaken consciousness or not. One may say, indeed, that inasmuch as under normal conditions the bronchial irritation always causes a movement of a particular group of muscles, there is to this extent a fixed pathway of discharge; but, as I have formerly explained, this is only an expression of the particular tension of particular centres, and is variable with that tension; the other centres are also affected, even when they are not excited to discharge.244Lallemand,Recherches sur L’Encéphale, III. 310.245West Riding Lunatic Asylum Reports, 1875, Vol. V. pp. 252,sq.246GalletSpurzheim,Anat. et Physiol. du Système Nerveux, I. 83.247Printed in theBritish and Foreign Medical Review, Jan. 1845.248Griesinger,Abhandlungen, 1872. The first volume contains a reprint of this memoir.249Landry,Traité des Paralysies, I. 55. Conf.Ziemssen,Choreain theHandbuch der speciellen Pathologie, Bd. XII. 2, p. 408. AndLuys,Études de physiol. et pathol. cérébrales, 1874, pp. 89–94.250Sue,Recherches Philosophiques sur la Vitalité et le Galvanisme, p. 9. He was not consistent, however, but adopted Bichat’s opinion respecting the sensibility of the viscera, p. 68.251Legallois,Expériences sur le principe de la vie. Published, I conclude, in 1811; the edition I use is the one printed in theEncyclopédie des Sciences Medicales, IV.252Wilson Philip,Experimental Inquiry into the Laws of the Vital Functions, pp. 209, 210.253Longet,Traité de Physiologie, II. 105.254He cites Cuvier, Majendie, Deamoulins, and Mayo as maintaining this error.255Grainger,Structure and Functions of the Spinal Cord, p. 66.256Nasse,Unters. zur Physiologie und Pathologie, Vol. II. Part 2.257Carus,System der Physiologie, III. 101.258J. W. Arnold,Die Lehre von der Reflex-Function, 86.

168Robin,Anat. et Physiol. Cellulaires, p. 335.

169Archives de Physiologie, 1872, p. 268.

170The fact of the existence of cells in the white substance is one which is very difficult of interpretation on the current hypotheses. The cells are found in regular columns and irregularly scattered.Bollthinks that while in the white substance of both cerebrum and cerebellum there are true nerve-cells as well as connective corpuscles, in the cord there are only the latter. But hitherto there has been no decisive test by which a nerve-cell can be distinguished from a connective corpuscle.

171Monthly Journal of Micros. Science, XI. 219. This accords with whatKupffersays respecting the entire absence of cells in the earliest stages observed by him in the sheep. The white substance of the spinal cord he describes as soft, transparent, and gelatinous, in which dark points are visible; these dark points are seen in longitudinal sections to arise from the fibrillation of the substance.—BidderundKupffer,Op. cit., p. 111.

172Weismann,Die nachembryonale Entwick. der Musciden, in theZeitschrift für Wissen. Zoologie, 1864, Bd. XIV. Heft III.

173The suggestion in the text has since received a striking confirmation in the observations ofSigmund Mayeron the regeneration of nerves. The nerve when divided rapidly undergoes fatty degeneration, which is succeeded by a transformation of the myeline and axis cylinder into a homogeneous mass; in this resolved pulp new longitudinal lines of division appear, which subsequently become new fibres, and new nuclei are developed in the remains of the untransformed substance.—Archiv für Psychiatrie, Bd. VI. Heft II.

174Strong confirmation of various statements in the text, since they were written, has been furnished by the researches ofEichhorst, published inVirchow’s Archiv, LXIV. Our knowledge of the development of nerve-tissue in human embryos is so scanty that these researches have a great value.Eichhorstdescribes the striation of the cells in the cord to begin only at the fourth month; up to this time they are, what I find most invertebrate cells to be, granular, not fibrillar. There is very slight branching of the cell processes until the ninth or tenth month, when the multipolar aspect first appears; the cells are unipolar up to the end of the fourth month. The connection between the white columns and the gray columns is very loose up to the fifth month; and the two are easily separated. Subsequently the union is closer. The substance of the white columns readily separates into bundles and fibres, but that of the gray columns falls into a granular detritus if attempted to be teased out with needles. But after the fifth month this is no longer so. Instead of a granular detritus there appears a network of fine fibres and fibrils. Although the white posterior columns are developed before the fifth month, not a single cell can be seen in the posterior gray columns until the second half of the ninth month. (Yet the fibres are imagined to arise in the cells!) The passage from the granular to the fibrillar state is the same in the cell substance and the neuroglia. The nerve-fibre, as distinguished from a naked axis cylinder, does not appear till the fourth month. It is at first a bipolar prolongation of the nucleus. As it elongates, the nucleus seems to sitonit, and so loosely that it is easily shifted away by pressure on the covering glass. Finally the fibre separates entirely from the nucleus, andthenbegins to clothe itself with the medullary sheath. Very curious is the observation that so long as the axis cylinder is naked it is never varicose, but with the development of the medulla the primitive axis becomes fluid.

175Mayer,Op. cit., 393. I cannot, however, agree withMayerwhen he says that the continuity of a nerve-fibre with a cell hasneverbeen distinctly shown (p. 395); in the Invertebrata and in the Electric fishes such a continuity is undeniable; and it has occasionally been seen in Vertebrata.

176Ranvier, in theComptes Rendus, 1875, Vol. LXXXI. p. 1276. This observation throws light on the fact that cell processes are sometimes seen entering nerve-roots (§124).The very remarkable observations of Mr.F. Balfour,On the Development of the Spinal Nerves in Elasmobranch Fishes(Philos. Trans., Vol. CLXVI. p. 1), show that the spinal root, ganglion, and nerve-trunk arise from histological changes in a mass of cells at first all alike;notthat ganglion-cells are formed and from their processes elongate into fibres. The nerve, he says, forms a continuation of its root rather than of its ganglion (p. 181); which accords withRanvier’sview.

176Ranvier, in theComptes Rendus, 1875, Vol. LXXXI. p. 1276. This observation throws light on the fact that cell processes are sometimes seen entering nerve-roots (§124).

The very remarkable observations of Mr.F. Balfour,On the Development of the Spinal Nerves in Elasmobranch Fishes(Philos. Trans., Vol. CLXVI. p. 1), show that the spinal root, ganglion, and nerve-trunk arise from histological changes in a mass of cells at first all alike;notthat ganglion-cells are formed and from their processes elongate into fibres. The nerve, he says, forms a continuation of its root rather than of its ganglion (p. 181); which accords withRanvier’sview.

177In theHandbuch der menschlichen AnatomieofW. Krause, which has just appeared, I am pleased to find a similar view, p. 376.

178On this point consultAxel KeyandRetzius, in theArchiv für mikros. Anat., 1873, p. 308, where the nutritive disturbance is assigned to the fact that the lymph can no longer take its normal course.Waller’sobservations on the degeneration of the optic nerves, with preservation of the integrity of the retina, after division of the nerves (Proceedings of Royal Society, 1856, p. 10), cannot be urged in support of his view, becauseBerlinandLebert’sobservations are directly contradictory of his.SaemischundGraefe,Handbuch der Augenheilkunde, II. 346. It is said byKrenchelthat if the nerves be divided, so as to prevent disturbances in the circulation, no peripheral degeneration takes place (cited byEngelmanninPflüger’s Archiv, 1875, p. 477).

179Schiff,Lehrbuch der Physiologie, pp. 120, 121.

180Kölliker,Gewebelehre, 317.Schwalbe,Archiv für mikros. Anat., 1868, p. 51.

181I was first shown this in 1858 by the late Prof.Harlessin Munich, who at the same time showed me that the nerve thus bared of its sheath, if left some hours in gastric juice, split up into regular discs, like the sarcous elements of muscles.

182Stieda,Bau des centralen Nervensystem der Amphibien und Reptilien, 1875, p. 41.

183Butzke, inArchiv für mikroskopische Anatomie, Bd. III. Heft 3, p. 596.

184Except in the rare cases where there is anastomosis of the muscle-fibres; as, for example, in the heart. [According toEngelmann’sremarkable researches, the muscles of the heart form a continuum, so that irritation is propagated from one to the other:Pflüger’s Archiv, 1875, p. 465. This is indubitably the case in the embryonic heart, asEckhardpointed out.] This I hold to be the main cause of its rhythmic pulsation after removal from the body. Whatever influence the ganglia may have in exciting this pulsation, such influence would be powerless were not the muscles so connected; as may be seen in the other organs which are richly supplied with ganglia, yet do not move spontaneously; and in organs (such as the ureter or the embryonic heart, and the hearts of invertebrata) which move spontaneously, yet have no ganglia.

185Schröder van der Kolk,Bau und Funktionen der Med. Spinalis, p. 67.

186It is very instructive to learn that for some six months or so the rat is quite incapable of correctlylocalizingthe pain.

187Vulpian,Leçons sur le Système Nerveux, p. 288. The experiment has been confirmed byRosenthal, and byBidder(Archiv für Anatomie, 1865, p. 246), who first (in 1842) attempted this union of different nerves, but arrived at negative results; as didSchiff(Lehrbuch der Physiol, 1859, p. 134) andGlugeetThiernesse(Annales des Sciences Naturelles, 1859, p. 181).

188Sachs, in theArchiv für Anat., 1874, pp. 195,sq.

189Laplace,Essai Philos. sur les Probabilités, p. 239.

190The mode of termination of nerves in muscles is still a point on which histologists disagree; probably because there is no abrupt termination, but a blending of the one tissue with the other. In the Tardigrades, for example, there is actually no appreciable distinction between nerve and muscle at the point of insertion of the nerve; and if in the higher animals there is an appreciable difference between nerve and muscle, there is an inseparable blending of undifferentiated substance at their point of junction. [According toEngelmann’srecent researches, there seems good reason to suppose that muscles are composed of contractile substance and a substance which is a modification of axis-cylinder substance; the first being doubly refracting, the second isotropic:Pflüger’s Archiv, 1875, p. 432.]

191Schiff,Lehrbuch, p. 73.

192Freusbergobserved that the reflex movements in the legs of a dog whose spine had been divided were considerably lessened after food or drink. They fell from 95 to 46 pendulum-beats in a minute after alitreof water had been drunk. See his instructive memoir,Reflex-Lähmungen beim Hunde, inPflüger’s Archiv, 1874, p. 369.

193M.Herzenthus describes the effects of stimulating the vagus with varying intensities: “Si l’on se sert de l’appareil de Dubois Raymond, on commence par appliquer une irritation tellement faible qu’elle ne produit aucun effet; on rapproche alors peu à peu lea deux bobines de l’appareil avec le plus grand soin, par fractions de centimètres, parmillimètress’il le faut, et l’on trouve ainsi le degré d’irritation qui accelère les battements du cœur et qui produit le maximum de pulsations dans l’unité de temps admise pour l’expérience. Quand on est là il suffitd’un millimètrede plus pour faire disparaître l’augmentation, un autre millimètre peut produire une diminution, et untroisièmepeut arrêter le cœur complètement. En reculant alors, en éloignant peu à peu les deux bobines,on rètourne à la force qui produit l’augmentation des battements.”Herzen,Expériences sur les Centres Modérateurs de l’Action Réflexe, 1864, p. 68. There have been serious doubts thrown on these experiments; but several experimenters have confirmed their exactness. Quite recently they have been confirmed byBulgheri,Il Morgagni, VIII.; and byArloingandTripier,Archives de Physiologie, 1872, IV. p. 418. It must be confessed, however, that the whole subject of the heart’s innervation is at present very imperfectly understood.

194Cayrade,Recherches sur les Mouvements Réflexes, 1864, p. 58.

195A frog’s brain is removed, and the body then suspended by the lower jaw, the legs are allowed to dip into a slightly acidulated liquid, the chemical action of which stimulates the skin.

196I saw a patient in the BerlinCharitéwhose face and left hand were in a constant state of convulsive twitching, but no sooner was a scar on the left hand (where the nerve had been divided) firmly pressed than the twitchings ceased, andpainwas felt; on removal of the pressure, pain ceased and the twitchings returned.

197Pflüger’s Archiv, 1875. No one interested in the Reflex Theory should omit a careful study of the papers byFreusbergandGoltz. I have drawn freely from them.

198SirJames Pagethas an interesting collection of facts which illustrate this Law of Arrest, in his paper on “Stammering with other Organs than those of Speech,”British Medical Journal, 1868, Vol. II. p. 437, reprinted in hisClinical Lectures and Essays, 1875, p. 77.

199Archives de Physiol., 1868, p. 157.

200West Riding Lunatic Asylum Reports, 1874, p. 200.

201Claude Bernard,Système Nerveux, I. 383.

202See the excellent remarks of Dr.Lauder Bruntonon this point in his paper on Inhibition in theWest Riding Lunatic Asylum Reports, 1874, p. 180.

203The interesting question of interference has been experimentally treated byWundtin his recently publishedMechanik der Nerven, 1876, and theoretically as wave-movement byMedem,Grundzüge einer exakten Psychologie, 1876.

204On the distinction between first notions and theoretic conceptions, seeProblems of Life and Mind, Vol. II. p. 277.

205Not transcendental anda priori, as Kant teaches; but immanent in Feeling.

206The reader will understand that although mechanical relations are modes of Feeling, as all other relations are, yet their aspect is exclusively objective, referring to objects ideally detached from subjects.

207Antoine Cros,Les Fonctions supérieures du Système nerveux, 1875, p. 85.

208The solution offered in the present chapter was first offered inProblems of Life and Mind, 1875, II. 465,sq.I mention this because since the publication of that volume other writers have expressed the same ideas, sometimes using my language and illustrations: e. g. M.Tainein theRevue Philosophique, January, 1877, art.,Les Vibrations cérébrales et la Pensée.

209Problems of Life and Mind, Vol. II. pp. 443 and 482.

210“The retinal image is the last effect known of the action of objects on us; what happens beyond the retina we know not; our knowledge of the objective process has at present here its limit.”—Ewald Hering,Beiträge zur Physiologie, 1862, p. 166. That is to say, we have a definite translation of the process in geometric terms as far as the retina, and thence onwards Geometry fails us, and Neurology and Psychology are invoked.

211CompareProblem II.Chap. IV.

212“Das Bewusstwerden ist nichts Anderes als ein weiter fortgeschrittenes Erinnern oder Neuwerden des von aussen aufgenommenen Wissens, ein innerliches Wissen dieses Wissens oder ein in sich reflectirtes Wissen.”—Jessen,Versuch einer Wissenschaftlichen Begründung der Psychologie, 1855, p. 477.

213In common language a stone or a tree is said to be unconscious; but this is an anthropomorphic extension of the term. In strictness we should no more speak of unconsciousness outside the sphere of Sentience than of darkness outside the sphere of Vision.

214The contraction may be effected in the eye out of the organism. See p.229. It is then no reflex.

215Glasgow Medical Journal, 1857, p. 451. See also further on,noteto p.426.

216Mayer,Die Elementarorganisation des Seelenorgans, p. 12, is the authority for the last statement.

217Allgemeine Zeitschrift für Psychiatrie, Bd. 31, p. 711.

218Aubert,Grundrüge der physiol. Optik, 1876, p. 633. “The accommodative movement of the eye is to be considered voluntary. It is true we contract the pupil without being conscious of the contraction of muscular fibres,but this holds good for every voluntary movement. When a person raises the tone of his voice he is not conscious that by muscular contraction he makes his chordæ vocales more tense; he attains his object without being aware of the means by which he does so. The same is applicable to accommodation for near objects and to the contraction of the pupil accompanying it. The fact thatthis last is only an associated movement does not deprive it of its voluntary character, for there is perhaps no single muscle which can contract entirely by itself.”Donders,On the Anomalies of Accommodation, 1864, p. 574. ProfessorBeerof Bonn has the rare power of contracting or dilating the pupils of his eye at will; here ideas act as motors. When he thinks of a very dark space the pupil dilates, when of a very bright spot the pupil contracts. (Noble,The Human Mind, 1858, p. 124.) I believe this to be only an exaggerated form of the normal tendency. In all of us the mechanism is so disposed that the feelings of dilatation are associated with feelings (and consequently ideas) of darkness; and by this association a reversal of the process obtains, so that the idea of darkness calls up the feeling it symbolizes.

219Spencer,Principles of Psychology, I. 499.

220Descartesexpressly calls them sensitive machines. He refuses them Thought, but neither “la vie ou le sentiment.” He adds, “Mon opinion n’est pas que les bêtes voient comme nous lorsque nous sentons que nous voyons.”—Œuvres, IV. p. 339. This example is cited by him in proof of human automatism: “Que ce n’est point par l’entremise de notre âme que les yeux se ferment, puisque c’est contre notre volonté, laquelle est sa seule ou du moins sa principale action; mais c’est à cause que la machine de notre corps est tellement composée que le mouvement de cette main vers nos yeux excite un autre mouvement en notre cerveau qui conduit les esprits animaux dans les muscles qui font abaisser les paupières.” All indeed that we assign to Sensibility, he assigns to these hypothetical animal spirits, and thence he concludes, “Qu’il ne reste rien en nous que nous devions attribuer à notre âme sinon nos pensées.”—Les Passions de l’Âme, art. 13 and 17. Comp.Discours de la Méthode, partie iv.

221Descartescompares the animal mechanism to that of the grottos and fountains at Versailles, the nerves to the water-tubes:—“Les objets extérieurs qui par leur seul présence, agissent contre les organes des sens, et qui par ce moyen, la déterminent à se mouvoir en plusieurs diverses façons, selon comme les parties du cerveau sont disposées, sont comme les étrangers, qui entrant dans quelques unes des grottes de ces fontaines causent euxmêmes sans y penser les mouvements qui s’y font en leur présence: car ils n’y peuvent entrer qu’en marchant sur certains carreaux tellement disposés, que s’ils approchent d’une Diane qui se baigne, ils la font cacher dans les roseaux; et s’ils passent outre pour la poursuivre, ils feront venir vers eux un Neptune qui les menacera de son trident; ou s’ils vont de quelque autre costé, ils en feront sortir un monstre marin qui leur vomira de l’eau contre la face.”—Traité de l’Homme, 1664, p. 12. Ingenious as the comparison is, it only illustrates how machines may be constructed to imitate animal actions. Diana always hides herself when a certain spot is trodden upon; and Neptune always appears when another spot is trodden upon. There is no fluctuation, no sensibility discerning differences and determining variations. Compare the following experiment: A monkey was placed on the table and a shrill whistle made close to its ear: “Immediately the ear was pricked and the animal turned with an air of intense surprise, with eyes widely opened and pupils dilated, to the direction whence the sound proceeded. On repetition of the experiment several times, though the pricking of the ear and the turning of the head and eyes constantly occurred, the look of surprise and dilatation of the pupils ceased to be manifested.”—Ferrier,The Functions of the Brain, 1876, p. 171. A mechanical monkey would always have reacted in precisely the same way on each stimulus.

222Printed in theFortnightly Review, November, 1874, from which all my citations are made.

223Schiff,Lehrbuch der Physiol., 1858, p. 212.Hermann,Physiology, translated byGamgee, 1875, p. 511.

224Meanwhile the reader is referred toSchröder van der Kolk,Pathologie der Geisteskrankheiten, 1863, p. 51; orJessen,Physiologie des menschlichen Denkens, 1872, p. 66.

225Griesinger,Les Maladies Mentales, p. 96.

226M.Luyscites the case of a patient who conversed quite rationally with a visitor “sans en avoir conscience, et ne se souvenait de rien”; and he draws the extraordinary conclusion that the conversation “s’opérait en vertu des forces réflexes.”—Études de Physiologie et de Pathologie Cérébrales, 1874, p. 117. Is it not obvious that the patient must have been conscious at the time, though the consciousness vanished like that in a dream? The persistent consciousness is the continuous linking on of one state with previous states—the apperception of the past.

227Abercrombie,Inquiries concerning the Intellectual Powers, 1840, p. 151.Wigan,The Duality of the Mind, 1844, p. 270.Despine,La Psychologie Naturelle, 1868, I. 54.

228Dr.Hughlings Jacksonhas quite recently cited some curious examples in his own practice. SeeWest Riding Lunatic Asylum Reports for 1875.

229Problems, Vol. II. p. 478,sq.

230“Le sentiment fait naître le mouvement, et le mouvement donne naissance au sentiment.”—Van Deen,Traités et Découvertes sur la Moëlle Épinière, 1841, p. 102.

231Dr.Carpentertells a similar story of AdmiralCodrington, who, when a midshipman, could always be awakened from the profoundest slumber if the word “signal” were uttered; whereas no other word disturbed him.

232Compare an interesting personal example given byJouffroy, quoted in SirW. Hamilton’sLectures, I. 331.

233Lancet, 10th July, 1858.

234Marshall HallinPhilos. Trans., 1833.Lectures on the Nervous System and its Diseases, 1836.New Memoir on the Nervous System, 1843.

235Müller,Physiology, I. 721.

236It is better simply to remove the brain, than to remove the whole head, which causes a serious loss of blood. An etherized animal may be operated on with ease and accuracy. For many experiments, mere division of the spinal cord is better than decapitation. Great variations in the results must be expected, because the condition of the animal, its age and sex—whether fasting or digesting—whether the season be spring or summer—and a hundred other causes, complicate the experiment.

237Volkmann, quoted byPflüger.

238Unzer,The Principles of Physiology(translated for the Sydenham Society), p. 235.

239Even so eminent an investigator asGoltzhas fallen into this confusion. He introduces an experiment to prove that the brainless frog is insensible to pain by the words “when an animal, placed under circumstances which would be very painful, makes no movement, although quite capable of moving, the least we can say is that it is improbable that the animal has sensation” (Nervencentren des Frosches, p. 127). I need not discuss the proof itself, having already done so inNature, Vol. IX. p. 84. The point to which I wish to call attention is the confusion of insensibility in general with insensibility to pain.

240SeeDuchenne,De Électrisation localisée, p. 398.Griesingercites various examples of insane patients who have burned the flesh off their bones while manifesting a total indifference to these injuries.Maladies Mentales, p. 94.Falretsays, “Nous avons vu plusieurs fois des aliénés s’inciser, s’amputer eux-mêmes diverses parties du corps sans paraître ressentir aucune souffrance.”Leçons cliniques de Médicine Mentale, 1854, I. 189. Patients incapable of feeling the contact of a hot iron with their skin have felt subjective burnings in the skin thus objectively insensible.

241Cros,Les Fonctions supérieures du Syst. nerveux, 1875, p. 27.

242Virchow’s Archiv, Bd. XXVIII. p. 30.

243The idea of afixed anatomical mechanismfor reflexion, such as that of an excito-motory system, is completely refuted by the fact that the gray substance may anywhere be cut sway, and yet so long as a small bridge of gray substance remains the stimulation will be propagated through it. The idea of afixed pathwayis also refuted by the fact of the variations in the reflex responses, and the necessary irradiation even for very simple reflexes. Take, for example, that of breathing. An irritation of the bronchial filaments is transmitted by the pneumogastric to its centre in the medulla oblongata; from this, however, it is immediately irradiateddownwardsto the cervical and dorsal regions, which innervate the muscles of chest and diaphragm, andupwardsto the brain, whether the stimulation awaken consciousness or not. One may say, indeed, that inasmuch as under normal conditions the bronchial irritation always causes a movement of a particular group of muscles, there is to this extent a fixed pathway of discharge; but, as I have formerly explained, this is only an expression of the particular tension of particular centres, and is variable with that tension; the other centres are also affected, even when they are not excited to discharge.

244Lallemand,Recherches sur L’Encéphale, III. 310.

245West Riding Lunatic Asylum Reports, 1875, Vol. V. pp. 252,sq.

246GalletSpurzheim,Anat. et Physiol. du Système Nerveux, I. 83.

247Printed in theBritish and Foreign Medical Review, Jan. 1845.

248Griesinger,Abhandlungen, 1872. The first volume contains a reprint of this memoir.

249Landry,Traité des Paralysies, I. 55. Conf.Ziemssen,Choreain theHandbuch der speciellen Pathologie, Bd. XII. 2, p. 408. AndLuys,Études de physiol. et pathol. cérébrales, 1874, pp. 89–94.

250Sue,Recherches Philosophiques sur la Vitalité et le Galvanisme, p. 9. He was not consistent, however, but adopted Bichat’s opinion respecting the sensibility of the viscera, p. 68.

251Legallois,Expériences sur le principe de la vie. Published, I conclude, in 1811; the edition I use is the one printed in theEncyclopédie des Sciences Medicales, IV.

252Wilson Philip,Experimental Inquiry into the Laws of the Vital Functions, pp. 209, 210.

253Longet,Traité de Physiologie, II. 105.

254He cites Cuvier, Majendie, Deamoulins, and Mayo as maintaining this error.

255Grainger,Structure and Functions of the Spinal Cord, p. 66.

256Nasse,Unters. zur Physiologie und Pathologie, Vol. II. Part 2.

257Carus,System der Physiologie, III. 101.

258J. W. Arnold,Die Lehre von der Reflex-Function, 86.

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